INFLUENCE OF TEMPERATURE. 99 
The reefs of the N avigator Islands were also sounded out, with others 
at the Society Group, besides numerous coral islands; and through all 
these regions no evidence was obtained of corals living at a greater 
depth than 15 or 20 fathoms. Within the reefs west of Viti Lebu 
and Vanua Lebu, the anchor of the Peacock was dropped sixty times 
in water from 12 to 24 fathoms deep, and in no case struck among 
growing corals; it usually sunk into a muddy or sandy bottom. 
Patches of reef were encountered at times, but they were at a less 
depth than 12 fathoms. By means of a drag, occasionally dropped in 
the same channels, some fleshy Alcyonia, and a few Hydroidea were 
brought up, but no reef-forming species. 
Outside of the reef of Upolu, corals were seen by the writer growing 
in twelve fathoms. Lieutenant Emmons brought up with a boat- 
anchor a large Dendrophyllia from a depth of fourteen and a half 
fathoms at the Feejees; and this species was afterwards found near 
the surface. Dendrophyllia, it may be remembered, is one of the 
deep-water genera. 
These facts, it may be said, are only negative, as the sounding-lead, 
especially in the manner it is thrown in surveys, would fail of giving 
decisive results. The character of a growing coral bed is so strongly 
marked in its uneven surface, its deep holes and many entangling 
stems, to the vexation of the surveyor, that in general the danger of 
mistake is small. But allowing uncertainty as great as supposed, 
there can be little doubt after so numerous observations over ex- 
tended regions of reefs. 
The depth of the water in harbours and about shores where 
there is no coral, confirms the view here presented. At Upolu, the 
depth of the harbours varies generally from twelve to twenty fathoms. 
On the south side of this island, Lieutenant Perry, off Falealili, one 
hundred yards from the rocky shores, found bare rocks in eighteen 
and nineteen fathoms, with no evidence of coral. ‘There is no cause 
here which will explain the absence of coral, except the depth of 
water ; for corals and coral reefs abound on most other parts of Upolu. 
Below Falelatai, of the same island, an equal depth was found with 
no coral. Off the east cape of Falifa harbour, on the north side of 
Upolu, Lieutenant Emmons found no cora', although the depth was 
but eighteen fathoms. About the outer capes of Fungasar harbour, 
Tutuila, there was no coral, with a depth of fifteen to twenty fathoms; 
and a line of soundings across from cape to cape afforded a bottom of 
sand and shells in fifteen to twenty-one and a half fathoms. About 
